Methods of using ionic liquids as corrosion inhibitors

ABSTRACT

Ionic liquid containing compositions may be used in the production, recovery and refining of oil and gas. In addition, they may be used to treat cooling water and/or to inhibit and/or prevent corrosion of metals.

FIELD

The disclosure relates to the use of ionic liquids as corrosioninhibitors.

BACKGROUND

Corrosion of metallic surfaces is often an acute problem which arisesduring the production and refining of hydrocarbon streams as well as inother industries which rely on aqueous fluids for the removal of heatfrom one medium to another. For instance, cooling towers extract wasteheat to the atmosphere by cooling of a water stream to a lowertemperature. Cooling towers are used in oil refineries, petrochemicaland other chemical plants, thermal power stations and power plants,steel mills, natural gas processing plants, food processing plants,semi-conductor plants as well as HVAC systems. Aqueous fluids, includingthose with high salt content, cause corrosion which may lead toequipment failure requiring equipment to be replaced. Corrosion alsodecreases plant efficiency due to loss of heat transfer. This is oftenthe result of heat exchanger fouling caused by the accumulation ofcorrosion products.

Highly corrosive conditions also arise during well stimulationoperations, such as pickling, acid washing, matrix acidizing and acidfracturing where aqueous acidic solutions are applied to the productionzone to increase the size of pores within the formation and to provideenlarged passageways for the flow of hydrocarbons.

Corrosive aqueous fluids having high salt content are also used indrilling and completion fluids. Marked corrosivity is often seen whensuch brines are used as packer fluids since they remain in contact withproduction tubing and casing for extended periods of time.

Concerns of corrosion also arise in the treatment of gas streams, suchas carbon dioxide and hydrogen sulfide, which generate highly acidicenvironments to which metallic surfaces become exposed. For instance,corrosion effects from brine and hydrogen sulfide are seen in flow linesduring the processing of gas streams. The presence of methanol, oftenadded to such streams to prevent the formation of undesirable hydrates,further often increases the corrosion tendencies of metallic surfaces.

Further, naturally occurring and synthetic gases are often conditionedby treatment with absorbing acidic gases, carbon dioxide, hydrogensulfide and hydrogen cyanide. Degradation of the absorbent and acidiccomponents as well as the generation of by-products (from reaction ofthe acidic components with the absorbent) results in corrosion ofmetallic surfaces.

Corrosion of metallic surfaces is evidenced by surface pitting,embrittlement and loss of metal. Pitting occurs when anodic and cathodicsites become stationary due to large differences in surface conditions.Once a pit is formed, the solution inside it is isolated from theenvironment and becomes increasingly corrosive with time. The highcorrosion rate in the pit produces an excess of positively charged metalcations, which attract chloride anions. In addition, hydrolysis produceshydrogen ions. The increase in acidity and concentration within the pitpromotes even higher corrosion rates, and the process becomesself-sustaining.

Various corrosion inhibitors for diminishing corrosive effects on metalsurfaces have been developed. Some corrosion inhibitors can have seriousconsequences. For instance, sulfur containing corrosion inhibitors maycause corrosion cracking which translates into tubular failures. Suchinhibitors further may decompose at elevated bottomhole temperatures andrelease hydrogen sulfide. The release of hydrogen sulfide as adecomposition product likely induces sulfide stress corrosion crackingof the alloy tubulars. Zinc based corrosion inhibitors have also beenused especially to address corrosive effects in cooling towers.Unfortunately, zinc salts, oxides and sulfates often precipitate incooling water. In alkaline waters, particularly above about pH 7.5,dissolved zinc tends to deposit or drop out. Thus, zinc salts are knownto be unstable in neutral or alkaline water. Scale formation furthertypically results from the metals in inorganic corrosion inhibitors. Forinstance, zinc scales typically form by use of zinc containing corrosioninhibitors. The effectiveness of corrosion inhibitors in aqueous systemsthus significantly decreases.

Efforts have been undertaken to find more effective corrosion inhibitorswhich do not render the negative effects of those previously seen. Forinstance, alternative corrosion inhibitors have been sought which arecapable of controlling, reducing or inhibiting corrosion withoutinducing sulfur-related corrosion cracking of metallic alloy tubulars.Further, there exists a need for improved compositions for inhibiting orpreventing corrosion in cooling water systems which are more effectiveand are more environmentally acceptable compositions.

SUMMARY

In an embodiment, the disclosure relates to the use of electronicallyneutral ionic liquids as corrosion inhibitors, the ionic liquidsrepresented by (I):

A⁺X⁻  (I)

wherein A is or contains nitrogen, a nitrogen containing heterocyclicring, is or contains phosphorus, or a phosphorus containing heterocycle;and X is an anion selected from the group consisting of halides;hydroxyl; hydroxyl containing nitrogen or sulfur compounds; sulfonates;sulfates; bisulfites; carbonates; alkyl carbonates; bicarbonates;thiocarbonates; dithiocarbonates; trithiocarbonates; xanthates,thiocyanates; alkoxides; carboxylates; hydroxycarboxylates; amino fattyacids; anionic alkoxylated fatty acids; anionic metallic complexes,sulfur or silicon containing anions; sulfides; polysulfides; anionicphosphate esters, anionic thiophosphate esters; anionic phosphonateesters; anionic thiophosphonate esters; alkyl substituted phosphines;anionic urea; anionic thiourea; anionic natural products; anionicthiols; anionic phenols; anionic phenol resins; anionic copolymers ofalpha olefins and maleic anhydride, esters, amides, imides orderivatives thereof; anionic acrylamido-methyl propane sulfonate/acrylicacid copolymers; anionic homopolymers, copolymers and terpolymers of oneor more acrylates, methacrylates, acrylamides and acids, optionallycopolymerized with one or more ethylenically unsaturated monomers;anionic phosphated maleic copolymers; an anionic homo or copolymer of anoxirane or methyloxirane and mixtures thereof or a zwitterion.

Another embodiment relates to the use of ionic liquids as corrosioninhibitors, the ionic liquids represented by (II) and (Ill):

R¹R²R³R⁴A⁺X⁻  (II);

R¹R²R³A⁺R⁸A⁺R⁵R⁶R⁷X⁻  (III)

wherein:

A in formula (II) is or contains nitrogen or phosphorus or aheterocyclic ring thereof and wherein each A in formula (III) isindependently selected from nitrogen or phosphorus or a heterocyclicring thereof; and

X is an anion selected from the group consisting of halides; hydroxyl;hydroxy containing nitrogen or sulfur compounds; carbonates; alkylcarbonates; bicarbonates; carboxylates; hydroxycarboxylates;dithiocarbonates; trithiocarbonates; xanthates, thiocyanates; alkoxides;anionic urea; anionic alkyl substituted phosphines; anionic amino fattyacids; anionic alkoxylated fatty acids; anionic acrylamido-methylpropane sulfonate/acrylic acid copolymers; anionic phosphated maleiccopolymers; anionic homo or copolymers of an oxirane or methyloxirane;anionic metal complexes; sulfur or silicon containing anions; anionicphosphate esters; anionic thiophosphate esters; anionic phosphonateesters; anionic thiophosphonate esters; anionic thiols; anionic naturalproducts; anionic phenols; anionic phenol resins; anionic copolymers ofalpha olefins and maleic anhydride, esters, amides, imides orderivatives thereof; anionic alkyl substituted phosphines; and anionichomopolymers, copolymers and terpolymers of one or more acrylates,methacrylates and acrylamides, optionally copolymerized with one or moreethylenically unsaturated monomers; and mixtures thereof; and furtherwherein R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are independently selected fromthe group consisting of hydrogen; benzyl; alkylbenzyl, or oxyalkyl(including —CH₂CH₂OH) or —CH₂CH(CH₃)OH); a straight or branched alkylgroup, an alkylbenzyl group, an arylalkyl group, a straight or branchedchain alkenyl group, a hydroxyalkyl group or a hydroxyalkylbenzyl group;and a polyoxyalkylene group; and R⁸ is a straight or branched alkylenegroup, an alkylene oxyalkylene, or an alkylene polyoxyalkylene or azwitterion; and further wherein R groups may be joined to form aheterocyclic nitrogen, sulfur or phosphorus containing ring.

In another embodiment, a method of enhancing the performance of acorrosion inhibitor is provided by contacting the corrosion inhibitorwith a corrosion inhibiting ionic liquid. In these instances, thecorrosion inhibiting ionic liquid may act as an intensifier for thecorrosion inhibitor; the corrosion inhibitor not being an ionic liquid.

DETAILED DESCRIPTION

The description provides specific details, such as material types,compositions, and processing conditions in order to provide a thoroughdescription of embodiments of the disclosure. Characteristics andadvantages of this disclosure and additional features and benefits willbe readily apparent to those skilled in the art upon consideration ofthe following detailed description of exemplary embodiments. Thedescription herein, being of exemplary embodiments, is not intended tolimit the scope of the claims.

As used herein and throughout various portions (and headings) of thispatent application, the terms “disclosure”, “present disclosure” andvariations thereof are not intended to mean every possible embodimentencompassed by this disclosure or any particular embodiment(s). Thus,the subject matter of each such reference should not be considered asnecessary for, or part of, every embodiment hereof or of any particularembodiment(s) merely because of such reference.

Certain terms are used herein and in the appended embodiments to referto particular components. As one skilled in the art will appreciate,different persons may refer to a component by different names. Thisdocument does not intend to distinguish between components that differin name but not function. Also, the terms “including” and “comprising”are used herein and in the appended embodiments in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to . . . .” Further, reference herein and in the appendedembodiments to components and aspects in a singular tense does not limitthe present disclosure or appended embodiments to only one suchcomponent or aspect, but should be interpreted generally to mean one ormore, as may be suitable and desirable in each particular instance.Thus, the use of the terms “a”, “an”, “the” the suffix “(s)” and similarreferences are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext.

All ranges disclosed herein are inclusive of the endpoints, and theendpoints are independently combinable with each other. Unless statedotherwise, any range of values within the endpoints is encompassed. Forexample, where the endpoints of a range are stated to be from 1 to 10,any range of values, such as from 2 to 6 or from 3 to 5 will be definedby the range.

All references are incorporated herein by reference.

The phrase “ionic liquid” refers to a neutral molten salt composedentirely of ions and which is liquid at ambient or near ambienttemperatures. The phrase shall include the quaternary organic salts of(I), (II) and (Ill). The ionic liquid functions as a corrosioninhibitor.

The phrase “second corrosion inhibitor” shall refer to any material(other than an ionic liquid) which enhances the performance of an ionicliquid or whose performance is enhanced by an ionic liquid.

The phrase “treatment composition” shall refer to a compositionresulting from contact of an ionic liquid with a second corrosioninhibitor. The phrase shall include blends, mixtures, complexes andreactions products of the ionic liquid and second corrosion inhibitor.

As used herein, unless otherwise restricted, “inhibit”, “inhibiting” or“inhibition” shall include the inhibition, prevention, reduction orcontrol of corrosion of a metallic surface.

The phrase “corrosion inhibitor” shall refer to a material capable ofinhibiting, preventing or reducing corrosion of a metallic surface.

As used herein, “petroleum hydrocarbon fluid” shall include crude oil,shale oil, shale gas condensate, bitumen, diluted bitumen (dil-bit),refinery fractions including distillates including gas oil cuts,finished fuel including diesel fuel, petroleum fuel and biofuel,finished petroleum products, residual oil, fuel gas, flare gas, propane,butane, liquefied petroleum gas (LPG), natural gas liquid (NGL) andcombinations thereof. The ionic liquids and treatment compositionsdescribed herein are especially useful in the treatment of crude oil,bitumen, diesel fuel, petroleum fuel, biofuel, residual oil, fuel gas,flare gas, propane, butane, liquefied petroleum gas (LPG), natural gasliquid (NGL) and refinery fractions (including gas oil cuts and lightlubricating oils) and combinations thereof. In addition, any of thesemay contain water, brines, gases such as hydrocarbon gases, or acombination thereof.

As used herein, the word “conduit” may refer to any pipeline, pipe,tubing, tubular, flow conduit, thoroughfare or other artery in which achemical, including a petroleum hydrocarbon fluid, travels or contacts.The word “vessel” shall include any equipment or container in which apetroleum hydrocarbon fluid is in contact, such as heat exchangers, etc.The conduit may, but not limited to, those composed of a metal, plasticor glass. The site of the “conduit” or “vessel” shall include, but notbe restricted to reservoirs, wells, pipelines, refineries, fluidprocessing or treatment facilities (including those where gas or oilproduction or treatment occur, chemical plants, thermal power stations,power plants, steel mills, natural gas processing plants, foodprocessing plants, semi-conductor plants and HVAC systems) as well asthoroughfares leading to or from any of the above.

The ionic liquids and treatment compositions described herein may beused during the production of crude oil and gas.

In addition, the ionic liquids and treatment compositions may be usedduring the recovery of petroleum hydrocarbon fluids from undergroundreservoirs.

The ionic liquids and treatment compositions are most useful during theproduction of oil and gas from a well and during in a refinery operationincluding light-ends recovery, solid waste and cooling water treatment,process-water treatment, cooling, storage, and handling, productmovement, hydrogen production, acid and tail-gas treatment and sulfurrecovery.

The ionic liquids and treatment compositions may also be used during thepurification or another treatment phase of an industrial product. Forinstance, the ionic liquids and treatment compositions may be used totreat cooling water streams. Such streams include produced water(aqueous fluids produced along with crude oil and natural gas duringfrom reservoirs water naturally present in oil and gas bearinggeological formations, aqueous fluids produced or used during theproduction of oil and gas from reservoirs or an industrial product,aqueous fluids produced during the refining of oil and gas or anindustrial product, aqueous fluids used during the refining of oil andgas or an industrial product, aqueous fluids used or produced duringtransit or storage of petroleum hydrocarbon fluids or an industrialproduct). Exemplary water streams include flowback water, degassed sourwater, boiler blowdown streams, cooling tower bleed-off/blowdown(originating from oil refineries, petrochemical and natural gasprocessing plants, other chemical plants, thermal power stations, powerplants, steel mills, food processing plants, semi-conductor plants andHVAC systems). Wastewater streams from industrial applications includemunicipal wastewater treatment facilities, streams in transit to or frommunicipal wastewater treatment facilities, tanning facilities, and thelike. Exemplary products removed during water treatments describedherein may include inorganic salts, polymers, breakers, frictionreducers, lubricants, acids and caustics, bactericides, defoamers,emulsifiers, filtrate reducers, shale control inhibitors, phosphorusions, ions of calcium, magnesium and carbonates, bacteria as well otherproduction chemicals.

The ionic liquids and treatment compositions may also be used within aconduit or vessel or introduced into a conduit or vessel. The ionicliquids and treatment compositions may also be used during transit ofpetroleum hydrocarbon fluids or an industrial product as well as duringstorage of petroleum hydrocarbon fluid or an industrial product.

The ionic liquid and treatment compositions are typically liquid atrelatively low temperature. While the ionic liquids are salts, theytypically exhibit high flash points, good solvency for other chemicalsand strong basicity.

Suitable ionic liquids as PIPPFLI are those of the formula (I):

A⁺X⁻  (I)

wherein A is or contains nitrogen or phosphorus, a nitrogen containingheterocyclic ring or a phosphorus containing heterocyclic ring; and X isan anion selected from the group consisting of halides; hydroxyl;hydroxy containing nitrogen or sulfur compounds; carbonates; alkylcarbonates; bicarbonates; dithiocarbonates; trithiocarbonates;xanthates, thiocyanates; alkoxides; carboxylates; hydroxycarboxylates;amino fatty acids; anionic alkoxylated fatty acids; anionic metalliccomplexes, sulfur or silicon containing anions; anionic phosphateesters, anionic thiophosphate esters; anionic phosphonate esters;anionic thiophosphonate esters; alkyl substituted phosphines; anionicurea; anionic thiourea; anionic natural products; anionic thiols;anionic phenols; anionic phenol resins; anionic copolymers of alphaolefins and maleic anhydride, esters, amides, imides or derivativesthereof; anionic acrylamido-methyl propane sulfonate/acrylic acidcopolymers; anionic polyacrylamides, anionic aminomethylatedpolyacrylamides, anionic homopolymers, copolymers and terpolymers of oneor more acrylates, methacrylates and acrylamides, optionallycopolymerized with one or more ethylenically unsaturated monomers;anionic phosphated maleic copolymers; an anionic homo or copolymer of anoxirane or methyloxirane and mixtures thereof or a zwitterion.

Further, ionic liquids of formula (II) or (III) may be used as thePIPPCFI ionic liquid:

R¹R²R³R⁴A⁺X⁻  (II);

R¹R²R³A⁺R⁸A⁺R⁵R⁶R⁷X⁻  (III)

wherein:

A in formula (II) is or contains nitrogen or phosphorus or aheterocyclic ring thereof and wherein each A in formula (III) isindependently selected from nitrogen or phosphorus or a heterocyclicring thereof; and

X is an anion selected from the group consisting of halides; hydroxyl;hydroxy containing nitrogen or sulfur compounds; carbonates; alkylcarbonates; bicarbonates; carboxylates; hydroxycarboxylates; sulfonates;sulfates; bisulfites; thiocyanates; dithiocarbonates; trithiocarbonates;xanthates, thiocyanates; carbamates; dithiocarbamates; sulfides;polysulfides; alkoxides; anionic urea; anionic alkyl substitutedphosphines; anionic amino fatty acids; anionic alkoxylated fatty acids;anionic acrylamido-methyl propane sulfonate/acrylic acid copolymers;anionic phosphated maleic copolymers; anionic homo or copolymers of anoxirane or methyloxirane; anionic metal complexes; sulfur or siliconcontaining anions; anionic phosphate esters; anionic thiophosphateesters; anionic phosphonate esters; anionic thiophosphonate esters;anionic thiols; anionic natural products; anionic phenols; anionicphenol resins; anionic homo or copolymer of oxirane or methyloxirane;anionic copolymers of alpha olefins and maleic anhydride, esters,amides, imides or derivatives thereof; anionic alkyl substitutedphosphines; anionic polyacrylamides; anionic aminomethylatedpolyacrylamide, and anionic homopolymers, copolymers and terpolymers ofone or more acrylates, methacrylates, acrylamides and acid; optionallycopolymerized with one or more ethylenically unsaturated monomers; andmixtures thereof; and further wherein R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ areindependently selected from the group consisting of hydrogen; benzyl;alkylbenzyl, or oxyalkyl (including —CH₂CH₂OH) or —CH₂CH(CH₃)OH); astraight or branched alkyl group, an alkylbenzyl group, an arylalkylgroup, a straight or branched chain alkenyl group, a hydroxyalkyl groupor a hydroxyalkylbenzyl group; and a polyoxyalkylene group; and R⁸ is astraight or branched alkylene group, an alkylene oxyalkylene, or analkylene polyoxyalkylene or a zwitterion; and further wherein R groupsmay be joined to form a heterocyclic nitrogen, sulfur or phosphoruscontaining ring.

In an embodiment, cation of (I), (II) or (III) is phosphorus or aphosphorus containing ring and X is an anion selected from the groupconsisting of hydroxyl; hydroxy containing nitrogen or sulfur compounds;bicarbonates; alkoxides; hydroxycarboxylates; silicon containing anions;anionic amino fatty acids; anionic alkoxylated fatty acids; anionicthiophosphonate esters; alkyl substituted phosphines; anionic urea;anionic thiourea; anionic natural products; anionic phenols; anionicphenol resins; anionic copolymers of alpha olefins and maleic anhydride,esters, amides, imides or derivatives thereof; anionic acrylamido-methylpropane sulfonate/acrylic acid copolymers; anionic homopolymers,copolymers and terpolymers of one or more acrylates, methacrylates andacrylamides, optionally copolymerized with one or more ethylenicallyunsaturated monomers; phosphated maleic copolymers; an anionic homo orcopolymer of an oxirane or methyloxirane and mixtures thereof.

In another embodiment, cation A of formula (I), (II) or (III) is orcontains nitrogen or a nitrogen heterocyclic ring and anion X isselected from the group consisting of silicon containing anions; anionicthiophosphonate esters; anionic natural products; anionic phenol resins;alkoxides; anionic copolymers of alpha olefins and maleic anhydride,esters, amides, imides or derivatives thereof or a mixture thereof;amino fatty acids; anionic alkoxylated fatty acids; alkyl substitutedphosphines; anionic urea; anionic thiourea; anionic acrylamido-methylpropane sulfonate/acrylic acid copolymers; anionic homopolymers,copolymers and terpolymers containing acrylamide units; anionicphosphated maleic copolymers; anionic oxirane or methyloxirane homo orcopolymers; and mixtures thereof.

In another embodiment, the ionic liquid represented by (II) or (III) hasa cation A of is nitrogen (for II) and each A in (III) is nitrogen asdefined herein and wherein X is an anion selected from the groupconsisting of anionic metallic complexes; sulfur or silicon containinganions; anionic phosphate esters; anionic thiophosphate esters; anionicphosphonate esters; anionic thiophosphonate esters; anionic thiols;anionic natural products; anionic phenols; anionic phenol resins;anionic copolymers of alpha olefins and maleic anhydride, esters,amides, imides or derivatives thereof amino fatty acids; anionicalkoxylated fatty acids; alkyl substituted phosphines; an oxirane ormethyloxirane homo or copolymer; anionic urea; anionic thiourea; anionicacrylamido-methyl propane sulfonate/acrylic acid copolymers; anionichomopolymers, copolymers and terpolymers containing acrylamide units;anionic phosphated maleic copolymers and mixtures thereof; and furtherwherein R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are independently selected fromthe group consisting of hydrogen; benzyl; alkylbenzyl, or oxyalkyl(including —CH₂CH₂OH) or —CH₂CH(CH₃)OH); a straight or branched alkylgroup, an alkylbenzyl group, an arylalkyl group, a straight or branchedchain alkenyl group, a hydroxyalkyl group or a hydroxyalkylbenzyl group;and a polyoxyalkylene group; and R⁸ is a straight or branched alkylenegroup, an alkylene oxyalkylene, or an alkylene polyoxyalkylene or azwitterion; and further wherein R groups may be joined to form aheterocyclic nitrogen, sulfur or phosphorus containing ring.

Preferred ionic liquids are those of (III) having structures R¹R²R³R⁴N⁺;R¹R²R³N⁺R⁸N⁺R⁵R⁶R⁷; S+R¹R²R³; R¹R²R³R⁴P⁺; and R¹R²R³N⁺R⁴P⁺R⁵R⁶R⁷.

In one preferred embodiment, anion X of (I), (II) or (III) is ahydroxide, bicarbonate, carbonate, alkyl carbonate or an alkoxide.

In a preferred embodiment, R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ of formula (II)and (III) are independently selected from the group consisting of astraight or branched C₁₋₃₀ alkyl group, a C₇₋₃₀ alkylbenzyl group, aC₇₋₃₀ arylalkyl group, a straight or branched C₃₋₃₀ alkenyl group, aC₁₋₃₀ hydroxyalkyl group, a C₇₋₃₀ hydroxyalkylbenzyl group, a zwitterion(such as those from oxyalkylation of an amine with an alkylene oxide; ora polyoxyalkylene group; and R⁸ is a straight or branched C₁₋₃₀alkylene, an alkylene oxyalkylene, or an alkylene polyoxyalkylene or Rgroups may be joined to form a heterocyclic nitrogen, sulfur orphosphorus ring; and the anion comprises halides, hydroxide,bicarbonate, carbonate, alkyl carbonates, alkoxides, carboxylates, or acombination thereof; and further wherein X⁻ is hydroxide, bicarbonate,carbonate, alkyl carbonates, alkoxides, carboxylates, or a combinationthereof. In an exemplary embodiment, A of formula (II) or (III) isnitrogen or a nitrogen containing heterocyclic ring and anion X anion isa hydroxide, bicarbonate, carbonate, alkyl carbonate or an alkoxide.

In another preferred embodiment, R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ of (II)and (III) are independently —H or a C₁₋₂₀ alkyl; wherein at least one(or at least two) of R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ is a C₂₋₂₀ alkyl,preferably a C₆₋₁₂ alkyl.

Exemplary ionic liquids of formulas (I), (II) and (III) include, but arenot limited to, those ionic liquids having a cation of dicocodimethylammonium and ditallowdimethyl ammonium. Further specific exemplary ionicliquids are dicocodimethyl ammonium hydroxide, benzyltrimethylammoniumhydroxide, ditallowdimethyl ammonium hydroxide, tributylmethylammoniummethyl carbonate, tetraethylammonium bicarbonate, tetrapropylammoniumhydroxide, coco dimethylethylammonium methyl carbonate, dodecyltrimethylammonium hydroxide, (2-hydroxyethyl) cocoalkyl ammoniumhydroxide (including dialkyl, trialkyl, tetralkyl derivatives likedicocodimethyl ammonium hydroxide cocotrimethyl ammonium hydroxide),cocodialkylammonium chloride derivatives (such as (oxydi-2,1-ethanediyl)bis(cocodimethylammonium) chloride), tri-n-butyl methylammonium methylcarbonate, tetrabutylammonium hydroxide, tallowtrimethyl ammoniumhydroxide, cocotrialkyl ammonium hydroxide (such as cocotrimethylammonium hydroxide), cocodialkylammonium chloride derivatives (such as(oxydi-2,1-ethanediyl) bis(cocodimethylammonium) chloride), hydrogenatedtallow trimethyl ammonium hydroxide, dihydrogenated tallow dimethylammonium hydroxide, oxydiethylene bis(cocodimethylammonium hydroxidehaving a structure represented by the formula:Coco(CH₃)₂N⁺(CH₂)₂O(CH₂)₂N⁺(CH₃)₂Coco (OH⁻)₂ or a combination comprisingat least one of the foregoing.

In some instances, the cation of (III) may be a polyamine, meaning thecation may have two or more nitrogen atoms (and in some cases up to 5nitrogen atoms). In some instances, one or more of the nitrogens of thepolyamine may be cationic such that the cation of (III) may be apolyamine containing two or more cationic sites (and in some cases up to5 cationic sites). In such cases, R⁸ may correspond to (—NR¹R²)_(y) or(—NR¹R²R³)_(y) wherein y corresponds to 1, 2 or 3 to render the numberof nitrogen sites and R¹, R² and R³ are as defined above. Specifically,y is 1 when A is a triamine, y is 2 when A is a tetramine and y is 3when A is a pentamine. Exemplary are cations of diethylenediamine,triethylenetetraamine, tetraethylenepentamine and (bis)hexamethylenetriamine. In other instances, where both of A arephosphorus in (III), the cation may consist of multiple cationic siteson the phosphorus wherein R⁸ may correspond to (—PR¹R²)_(y) or(—PR¹R²R³)_(y) wherein y corresponds to 1, 2 or 3 to render the numberof phosphorus sites and R¹, R², and R³ are as defined above.

As used herein, the term “alkyl” refers to a straight or branched chain,saturated monovalent hydrocarbon group regardless whether straight orbranched chain is specifically mentioned or not; “aryl” refers to anaromatic monovalent group containing only carbon in the aromatic ring orrings; “arylalkyl” refers to an alkyl group that has been substitutedwith an aryl group, with benzyl being an exemplary arylalkyl group;“alkylbenzyl” refers to a benzyl group that has been substituted with analkyl group in the aromatic ring; “hydroxyalkyl” refers to an alkylgroup that has been substituted with a hydroxyl group with2-hydroxyethyl as an exemplary hydroxyalkyl group; “hydroxyalkylbenzyl”refers to a benzyl group that has been substituted with a hydroxyalkylgroup as defined herein in the aromatic ring; “alkylene” refers to astraight or branched chain, saturated, divalent hydrocarbon group, and“alkenyl” refers to a straight or branched chain monovalent hydrocarbongroup having at least two carbons joined by a carbon-carbon double bond.The term “substituted” as used herein means that at least one hydrogenon the designated atom or group is replaced with another group, providedthat the designated atom's normal valence is not exceeded. Substitutedwith a group means substituted with one or more groups.

Suitable nitrogen containing heterocyclic rings referenced hereininclude pyridinium, imidazolinium and a pyrrole cation (includingalkylated derivatives thereof). Further reference to “nitrogen” shallinclude nitrogen containing cations such as an oxyalkylated nitrogen.

In an embodiment, the cation of (I), (II) or (III) is a quaternary aminesalt, triethanolamine methyl chloride, oxyalkylated amine, polyamine,oxyalkylated polyimines, cationic melamine acid colloid or an oxyaminesuch as those of the formula (CH₃)₂N(CH₂)_(x)OH where x is 1 to 6,preferably 2.

As used herein, a polyoxyalkylene group has a formula

where each occurrence of R¹ is independently a C₁₋₁₀ alkylene or C₂₋₈alkylene, specifically ethylene, propylene, butylene, or a combinationthereof, and z is an integer greater than 1 such as 2 to 30, 4 to 25, or8 to 25.

An alkylene polyoxyalkylene group has a formula

wherein R² is a 01-30 alkylene, each occurrence of R³ is independently aC₁₋₁₀ alkylene or C₂₋₆ alkylene, specifically ethylene, propylene,butylene, or a combination thereof, and y is an integer from 1 to 500,such as 2 to 30, 4 to 25, or 8 to 25.

An alkylene oxyalkylene group has a formula of —R⁷—O—R⁸—, wherein R⁷ andR⁸ are each independently a C₁₋₂₀, or C₁₋₁₀, or C₁₋₅ branched orstraight chain alkylene. Optionally, R⁷ and R⁸ can be ethylene.

Exemplary halides for the anion X⁻ are —Cl, —Br, —F and —I. In anembodiment —Cl is preferred.

Suitable sulfur and phosphorus containing anions include sulfates (SO₄⁻), bisulfate (HSO₄ ⁻), thiocyanate (SCN⁻), thiocarbonate

dithiocarbamates

wherein R₁ and R₂ are independently selected from C₁₋₂₀ alkyl groups,xanthates

wherein R is a C₁₋₂₀ alkyl, sulfides (RS⁻) wherein R is a C₁₋₂₀ alkyl,anionic polysulfides (RS(S)_(x)S⁻) wherein R is a C₁₋₂₀ alkyl and x isone to five, anionic phosphate esters [ROP(═O)(OH)₂] and anionicphosphonate ester [R—P(═O)(OH)₂ (wherein R is a C₁₋₂₀ alkyl or a C₁₋₂₀oxyalkyl-(RO—); anionic thiophosphate esters

as well as anionic thiophosphonate esters (wherein R is a C₁₋₂₀ alkyl ora C₁₋₂₀ oxyalkyl- (RO—); sulfonates (RSO₃ ⁻) wherein R is C₁₋₂₀ alkyl oraryl or alkylaryl group; and anionic thiols (RSH) where R is —(CH)_(x))Hand x is from 1 to 4.

Exemplary oxirane or methyloxirane homo or copolymers include thosecontaining units of the structure —(CH₂CH₂O)_(x)CH₂CH(CH₃)O)_(y) where xand y are independently selected from 1 to 1500.

Exemplary anionic metal complexes in formulae (I), (II) and (Ill) mayinclude, but not be limited to Fe (such as Fe containing anions likeFeCl₄ ⁻), aluminum (such as Al containing anions like AlCl₄ ⁻), etc.Further, the anionic metal complex may be formed from copper, zinc,boron, tin and mixtures thereof.

The anion may further be an anionic natural products like anions of apolysaccharide, polyphenol or lignin. Suitable anions of polysaccharidesinclude anionic starches (such as mixtures of amylose and amylopectin),anionic polyphenols (such as anionic flavonoids or anionic naturalpolyphenols and anionic tannins (such as water soluble anionicpolyphenols with a molecular weight between 500 and 3,000).

Suitable anions may also be anionic phenolics such as anionic phenols,anionic alkyl substituted phenols, anionic phenol oxyalkylates, anionicalkyl substituted phenol oxyalkylates, anionic phenolic or alkylphenolresins and anionic phenol resin oxyalkylates. Typically, the alkylgroups of the anionic phenolics are C₁₋₂₈.

The anion may also be an alkoxide. Suitable alkoxides include those ofthe formula RO— where R is a C₁₋₃₀ alkyl or cycloalkyl group. In anembodiment, R is C₁₋₁₈ alkyl, C₆₋₁₂ aryl, or C₅₋₁₂ cycloalkyl, Exemplaryalkoxides are tert-butoxide, n-butoxide, isopropoxide, n-propoxide,isobutoxide, ethoxide, methoxide, n-pentoxide, isopentoxide,2-ethylhexoxide, 2-propylheptoxide, nonoxide, octoxide, decoxide andisomers thereof. Preferably, the alkoxides are tert-butoxide,isopropoxide, ethoxide, or methoxide. Tert-butoxide and methoxide arespecifically mentioned. The alkoxides may further be anionic ethylene orpropylene oxide homopolymers, anionic copolymers or terpolymers (whichmay optionally be crosslinked). Suitable crosslinking agents includebisphenol A or maleic anhydride.

Suitable alkyl carbonates are those of the formula ROCO₂ ⁻, where R is ahalogenated or non-halogenated linear or branched alkyl, or hydroxylalkyl group, preferably a halogenated or non-halogenated linear orbranched C₁₋₈ or C₁₋₅ alkyl group.

Exemplary carboxylates include formate, acetate, propionate, benzoate,n-butyrate, isobutyrate, pivalate, octanoate and laurate, as well asanions of C₁₈ fatty acids such as oleate, linolate and stearate.Exemplary hydroxycarboxylates include glycolate, lactate, citrate,glucarate, gluconate and tartrate.

Suitable anionic copolymers of alpha olefins and maleic anhydride,esters, amides, imides (and derivatives thereof) include those of thegeneral structure

where R is a C₁₋₃₀ alkyl group.

Suitable alkyl carbonates, carboxylates, anionic metal complexes,anionic natural products, anionic phenolics, alkoxides, anionic alphaolefin/maleic anhydride polymers, anionic polymers of acrylates,methacrylates and acrylamides and sulfur cations are those referenced inthe paragraphs above.

The ionic liquids of (I), (II), and (III) are salts having a meltingpoint range of −100° C. to 200° C., typically below 100° C. They aregenerally non-volatile and exhibit low vapor pressures and areenvironmentally more benign than other organic solvents, such asvolatile aromatics and alkanes. They are thermally stable over a widetemperature range with some having a liquid range of up to 300° C. orhigher. Typically they are molten salts of organic compounds or eutecticmixtures of organic and inorganic salts. Stability and other fundamentalphysical properties of the ionic liquids are influenced by the selectionof cation while the selection of anion generally determines thefunctionality of the ionic liquid.

In an exemplary embodiment, ionic liquids disclosed herein may beprepared by first forming a quaternary salt followed by ion exchangewith an acid or salt or by an anionic metathesis reaction with anappropriate anion source to introduce the desired counter anion. As anexample, a nitrogen or phosphorus containing heterocyclic compound (suchas an imidazole or pyridine) may first react with an alkylating agent toform the quaternary salt. The alkylating agent may be an alkyl chlorideproviding a broad range of alkyl groups on the nitrogen includingstraight and branched or cyclic C₁-C₂₀ alkyl groups. The quaternary saltmay then be subjected to ion exchange with an acid or salt to form theionic liquid.

Ionic liquids (I), (II) and (III) may be tailored by varying the cationand anion pairing may be combined with a second corrosion inhibitor toform a treatment composition. In some instances, the amount of ionicliquid in the treatment composition may be from about 3 to about 99weight percent.

In an embodiment, the anion of the ionic liquid may be the same as theconjugate base of the second corrosion inhibitor. For instance, asuitable ionic liquid may be prepared of formula (II) or (Ill) where thecation is nitrogen, each of R₁, R₂, R₃ and R₄ are hydrogen and anion Ais a phosphonate. The ionic liquid functions as a corrosion inhibitor.The treatment composition may consist of the ionic liquid and the secondcorrosion inhibitor. The conjugate base of the second corrosioninhibitor is a phosphonate, the same as the anion of the ionic liquid.

In some cases, corrosion inhibition improves when the ionic liquid isused in combination with the second corrosion inhibitor. The presence ofthe ionic liquid in the treatment composition may boost the corrosioninhibition power of the second corrosion inhibitor. (Likewise, thepresence of the second corrosion inhibitor in the treatment compositionmay boost the corrosion inhibition power of the ionic liquid.) Thecombination of ionic liquid and second corrosion inhibitor may thereforesubstantially reduce the amount of corrosion and rate of corrosion ontothe metallic surface compared to when a fluid containing only one of theionic liquid or second corrosion inhibitor is used. In one non-limitingexample, the presence of the ionic liquid in the treatment compositiondecreases the rate of corrosion onto a metallic surface by at least 25%and sometimes 50% or higher.

The ionic liquids and/or treatment compositions described herein mayexhibit multiple functions. For example, an ionic liquid(s) or treatmentcomposition(s) may be effective as a scale inhibitor as well as acorrosion inhibitor.

One or more ionic liquids and/or treatment compositions may beconcurrently used.

The second corrosion inhibitor is preferably a liquid material. If theinhibitor is a solid, it may be dissolved in a suitable solvent, thusmaking it a liquid.

The ionic liquid and treatment compositions are typically introduced totheir targeted location in an organic solvent or in an aqueous fluidsuch as fresh water, brackish water, brine as well as salt-containingwater solutions such as sodium chloride, potassium chloride and ammoniumchloride solutions. Suitable organic solvents include alkyl alcoholssuch as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcoholand butyl alcohol and alkylene glycols like ethylene glycol, propyleneglycol. The fluid containing the ionic liquid or treatment compositionmay further contain one or more surfactants, mutual solvents,sequestering agents, friction reducers, gelling agents, and otherconventional additives as well as mixtures thereof.

The amount of ionic liquid or treatment composition in the organicsolvent or aqueous fluid is dependent on the corrosive conditions,temperature and intended time of contact. Typically, the amount of ionicliquid or treatment composition in the fluid introduced to the targetedsite is from 1 ppm to about 5,000 ppm, or about 1 ppm to about 500 ppm,or about 5 ppm to about 150 ppm.

In an embodiment an effective corrosion inhibiting or preventativeamount of the ionic liquid or treatment composition is introduced to anacidic fluid prior to introduction of the acidic fluid into a targetedwell or conduit. This may especially be the case where the ionic liquidor treatment composition is used during a well treatment operation asdiscussed below.

When use of a treatment composition is desired, the ionic liquid andsecond corrosion inhibitor are first combined and then introduced intothe targeted location in the organic solvent or aqueous fluid. At timeshowever, the ionic liquid and second corrosion inhibitor may beintroduced in different stages.

The ionic liquid and treatment compositions dramatically inhibits theamount of corrosion and the rate of corrosion on metallic surfacedcaused by aqueous acids including mineral acids, like hydrochloric acid,hydrofluoric acid, sulfuric and phosphoric acids as well as weak acids,such as formic acid, acetic acid, hydroxyacetic acid, citric acid,phosphonic acid, methanesulfonic acid and propionic acid as well asother acids affecting industrial operations.

Inhibition of corrosion may be seen on a wide host of metallic surfacesincluding iron, chromium, ferrous base metals, alloys of steel, alloysof nickel, duplex steels, stainless steel, chrome steel, martensiticalloy steel, ferritic alloy steel, carbon steel, precipitation-hardenedstainless steels and the like. Pitting is dramatically reduced when theionic liquids and treatment compositions are used.

The ionic liquids and treatment compositions may be contacted with ahydrocarbon-containing stream under severe conditions of heat, pressure,agitation and/or turbulence. They may be used at a wide variety oftemperatures, typically ranging from 120° F. to 180° F. as well as up to350° F. beyond.

The ionic liquids and treatment compositions are very useful in theinhibition of corrosion of metallic surfaces during well treatmentoperations. The treated well may be a hydrocarbon producing well, suchas a gas or oil well, or non-hydrocarbon producing wells, such as waterinjection wells, water producing wells or geothermal wells. They can beused during various types of treatment operations that occur in orbefore the wellbore and in subterranean formation applications. Forexample, they can be used in pickling a tubular, cleaning a wellbore,scale treatment, and coiled tubing applications. They can also be usedin matrix acid stimulation, acid fracturing, acid tunneling, drillingmud removal, scale treatment, coiled tubing application, or damageremoval. Any known method of introducing the ionic liquid(s) ortreatment composition(s) into the reservoir can be used. In all of theseapplications, the ionic liquids and treatment compositions protect metaltubulars and alloy surfaces from acidic fluids that are introduced orproduced downhole.

The ionic liquids and treatment compositions can also be used to inhibitcorrosion during refining of hydrocarbon fluids, during transport orstorage of the fluids or during any period in between.

Further, the ionic liquids and treatment compositions are highly usefulin the prevention or inhibition of corrosion attributable to carbondioxide and hydrogen sulfide. The hydrogen sulfide may be formed whenthe treating acid contacts a sulfur-containing mineral, such as ironsulfide.

The ionic liquids and treatment compositions are further particularlyeffective in the treatment of cooling towers relying on aqueous fluidsfor the removal of heat from one medium to another. As such, the ionicliquids and treatment compositions may be used in oil refineries,petrochemical and other chemical plants, thermal power stations andpower plants, steel mills, natural gas processing plants, foodprocessing plants, semi-conductor plants as well as HVAC systems.

Exemplary ionic liquids as corrosion inhibitors include those wherein Xin (I), (II) or (Ill) is an anionic phosphate ester, anionicthiophosphate ester, anionic phosphonate ester; anionic thiophosphonateester; anionic diphosphonic acid; and anionic carboxylic acids (such asanionic glucaric acid).

Exemplary corrosion inhibitors further those wherein the cation ispyridinium or an imidazolinium as well as quat ammonium halides such asquat ammonium chlorides.

Other corrosion inhibitors include hydroxyl containing nitrogen orsulfur compounds such as alkylated thiols such as those of the formulaHS(CH₂)_(x)OH where x is from 1 to 8, like HSCH₂CH₂OH; anionic sulfonylalcohols such as 2-(methylsulfonyl) ethanol; 2-sulfanylethanol;2-sulfanyl, propan-1-ol; 2-sulfanylbutan-2-ol; 1-sulfanylbutanol-2-oland mixtures thereof.

Exemplary ionic liquids include those of structure (IV):

wherein R is a C₁₂-C₁₈ alkyl or alkenyl group and X is —OH, NH₂ orC(═O)R; exemplary phosphate esters or thiophosphate esters are thosehaving one of structures (VA) or (VB):

wherein R is an alkyl or RO(CH₂CH₂O)_(n)CH₂CH₂) and R″ and R′″ areindependently selected from —H and a C₁-C₂₀ alkyl; exemplary quatammonium chlorides are those of structure (VI):

wherein the alkyl group may contain from 1 to 20 carbon atoms; andexemplary alkyl pyridine quats are those of structure (VII):

wherein R is a C₁-C₁₈ alkyl or benzyl. In an embodiment, more than one Rgroup can be a substituent to the pyridinyl ring. In such case, thesecond R group is typically a C₁-C₁₂ alkyl group.

Further exemplary corrosion inhibitors include thiazoles, triazoles andthiadiazoles such as benzotriazole, tolyltriazole, octyltriazole,decyltriazole, dodecyltriazole, 2-mercaptobenzothiazole,2,5-dimercapto-1,3,4-thiadiazole,2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazoles,2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazoles,2,5-bis(hydrocarbylthio)-1,3,4-thiadiazoles, and2,5-(bis)hydrocarbyldithio)-1,3,4-thiadiazoles.

Suitable anionic groups for anion X of formula (I), (II) and (III)include the counter anions of any of the corrosion inhibitors referencedabove. For example, anion X of ionic liquid of formula (I), (II) and(III) may be an anionic phosphate ester, anionic thiophosphate ester,anionic phosphonate ester, anionic thiophosphonate ester, an anionicthiol, etc.

In a preferred embodiment, a treatment composition may be used for theinhibition, prevention or reduction of corrosion of metals; thetreatment composition comprising the ionic liquids set forth above andone or more corrosion inhibitors (other than an ionic liquid). Exemplarycorrosion inhibitors include those set forth in the paragraphs above. Inan embodiment, the anion X of the formula (I), (II) and (III) of thetreatment composition may be the same anion as the counter anion of thecorrosion inhibitor. For example, the treatment composition may contain(as corrosion inhibitor), the ionic liquid of (II) wherein R¹, R², R³and R⁴ are hydrogen and anion X is the counter cation of (I) above.

Pitting of metallic surfaces decreases when metallic surfaces arecontacted with the ionic liquids and/or corrosion inhibiting treatmentcompositions described in the paragraphs above.

Further, corrosion inhibiting treatment compositions have been noted toprovide a synergistic effect compared to the ionic liquid or thecorrosion inhibitor by themselves. i.e., inhibition, prevention and/orreduction of corrosion significantly increases when fluids are contactedwith a corrosion inhibiting treatment composition versus contacting ofthe metallic surface with the ionic liquid or corrosion inhibitor bythemselves.

EXAMPLES

All percentages set forth in the Examples are given in terms of weightunits except as may otherwise be indicated.

Example 1

An anion exchange method was followed to prepare sulfur based ionicliquids. A general procedure for the anion exchange method was followedwherein about 1 gram of KOH was dissolved in 5 grams methanol. About1.36 grams 2-mercaptoethanol was added while stirring at 60° C. for 15minutes. About 5 grams of a solution of N-benzyl, 2 methyl pyridiniumchloride (75%) in methanol (25%) was then added dropwise and the mixstirred at 60° C. After 30 minutes of stirring, the solution wasfiltered while still hot to remove the potassium chloride by-product.The product was characterized by the replacement of the chloride on thepyridinium by the mercaptide of the 2-mercaptoethanol.

A second procedure which avoided the need to filter the product. Thefollowing general procedure was followed. About 1.36 grams of2-mercaptoethanol was added with stirring at room temp to 8 grams 55%aqueous tetrabutylammonium hydroxide. A slight exotherm occurred onmixing. The mixture was stirred for 15 minutes at 60° C. before 27 gramsof a solution containing 36% oxydi-2,1-ethanediyl)bis(cocodimethylammonium) dichloride in 30% water & 30% methanol wasadded dropwise. The solution was stirred for 30 minutes at 60° C. andcooled and used in all testing without further modification. Nofiltration was required as the tetrabutylammonium chloride by-productformed in the reaction was soluble in the product.

The synthesis of ionic liquids may be illustrated as follows:

A kettle test run was under the conditions of 10 ppm additive in a brinewith a carbon dioxide sparge, run for 18 hours at 180° F. and thecorrosion rate (CR) monitored using linear polarization resistance (LPR)probes. The results are set forth in Table I.

TABLE I Additive Dose 17.8 Additive (ppm) Hour CR Untreated None 273(303) oxydi-2,1-ethanediyl) bis(cocodimethyl- 10 233 ammonium)dichloride (ODEBCAC) 2 mercaptoethanol (2ME) 10 76 ODEBCAC/2ME 1:2 salt10 12 (8) ODEBCAC/2ME 1:1 salt 10 12 N-Octyl pyridinum/2 ME salt 10 11(8) N-Dodecyl pyridinium/2 ME salt 10 1 (2) N-Hexadecyl pyridinium/2 MEsalt 10 1 (2) N benzyl 2 methyl pyridinium chloride 10 279 (NBMPC)NBMPC/2 ME salt 10 4 (4) NBMPC + sodium trithiocarbonate 2:1 10 49 saltNBMPC + 1,8-Dimercapto-3,6-dioxa- 10 10 octane (DMDO) 2:1 salt NBMPC +DMDO 1:1 salt 10 10

Example 2

A neutralization procedure was used to prepare ionic liquids. Thegeneral procedure for all tests may be represented by preparation oftetra-n-butylammonium bitartrate (1:1 salt) wherein tartaric acid (10grams, 0.067 moles) was added in portions to a stirred solution of 55%aqueous tetra-n-butylammonium hydroxide (31.6 grams, 0.067 mole). Aslight exotherm occurred during the addition. The solution was stirredat room temperature for an additional 30 minutes before testing withoutfurther modification. The samples were then subjected to a kettle testusing synthetic cooling water and the corrosion rate was monitored usinglinear polarization resistance (LPR) probes. The results are set forthin Table II.

TABLE II Corrosion Rate Active Dose @ 18 hours Additive (ppm) (MPY)Tetra-n-butylammonium bi-tartrate 98 ″ 65 3.7 Tetramethylammoniumbi-tartrate 71 5.7 ″ 47 5.0 Tetraethylammonium bi-tartrate 60 3.9 Ethyltrimethylammonium b-tartrate 57 3.3 ″ 38 19.0 Benzyltrimethylammoniumbi-tartrate 45 12.4 Dodecyltrimethylammonium bi-tartrate 98 16.3(2-hydroxyethyl)trimethylammonium bi- 65 2.2 tartrateTetra-n-butylammonium citrate 1:1 salt 90 0.8 Tetraethylammonium citrate2:1 salt 90 1.0 Tetraethylammonium citrate 1:1 salt 110 1.6Tetra-n-butylammonium bi-glucarate 86 2.0 (1:1 salt) Tetraethylammoniummalate 1:1 salt 100 23.9 (2-hydroxyethyl)trimethylammonium 90 33.8citrate 1:1 salt (2-hydroxyethyl)trimethylammonium 90 37.1 citrate 2:1salt

What is claimed is:
 1. A method of inhibiting corrosion of a metallicsurface in contact with an acidic or aqueous fluid comprising contactingthe acidic or aqueous fluid with a corrosive inhibiting effective amountof an ionic liquid of the formula:A⁺X⁻  (I) wherein A is or contains nitrogen, phosphorus or aheterocyclic ring thereof; and X is an anion selected from the groupconsisting of halides; hydroxyl; hydroxy containing nitrogen or sulfurcompounds; carbonates; alkyl carbonates; bicarbonates; dithiocarbonates;trithiocarbonates; xanthates, thiocyanates; alkoxides; carboxylates;hydroxycarboxylates; amino fatty acids; anionic alkoxylated fatty acids;anionic metallic complexes, sulfur or silicon containing anions; anionicphosphate esters, anionic thiophosphate esters; anionic phosphonateesters; anionic thiophosphonate esters; alkyl substituted phosphines;anionic urea; anionic thiourea; anionic natural products; anionicthiols; anionic phenols; anionic phenol resins; anionic copolymers ofalpha olefins and maleic anhydride, esters, amides, imides orderivatives thereof; anionic acrylamido-methyl propane sulfonate/acrylicacid copolymers; anionic polyacrylamide; anionic homopolymers,copolymers and terpolymers of one or more acrylates, methacrylates andacrylamides, optionally copolymerized with one or more ethylenicallyunsaturated monomers; phosphated maleic copolymers; an anionic homo orcopolymer of an oxirane or methyloxirane and mixtures thereof or azwitterion.
 2. A method of inhibiting corrosion of a metallic surface incontact with an acidic or aqueous fluid comprising contacting the acidicor aqueous fluid with a corrosive inhibiting effective amount of anionic liquid of the formula:R¹R²R³R⁴A⁺X⁻  (II);R¹R²R³A⁺R⁸A⁺R⁵R⁶R⁷X⁻  (III) wherein: A in formula (II) is or containsnitrogen or phosphorus or a heterocyclic ring thereof and wherein each Ain formula (III) is independently selected from nitrogen or phosphorusor a heterocyclic ring thereof; and X is an anion selected from thegroup consisting of halides; hydroxyl; hydroxy containing nitrogen orsulfur compounds; carbonates; alkyl carbonates; bicarbonates;carboxylates; hydroxycarboxylates; dithiocarbonates; trithiocarbonates;xanthates, thiocyanates; alkoxides; anionic urea; anionic alkylsubstituted phosphines; anionic amino fatty acids; anionic alkoxylatedfatty acids; anionic acrylamido-methyl propane sulfonate/acrylic acidcopolymers; anionic phosphated maleic copolymers; anionic homo orcopolymers of an oxirane or methyloxirane; anionic metal complexes;sulfur or silicon containing anions; anionic phosphate esters; anionicthiophosphate esters; anionic phosphonate esters; anionicthiophosphonate esters; anionic thiols; anionic natural products;anionic phenols; anionic phenol resins; anionic polyacrylamides; anioniccopolymers of alpha olefins and maleic anhydride, esters, amides, imidesor derivatives thereof; anionic alkyl substituted phosphines; andanionic homopolymers, copolymers and terpolymers of one or moreacrylates, methacylates and acrylamides, optionally copolymerized withone or more ethylenically unsaturated monomers; and mixtures thereof;and further wherein R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are independentlyselected from the group consisting of hydrogen; benzyl; alkylbenzyl, oroxyalkyl; a straight or branched alkyl group, an alkylbenzyl group, anarylalkyl group, a straight or branched chain alkenyl group, ahydroxyalkyl group or a hydroxyalkylbenzyl group; and a polyoxyalkylenegroup; and R⁸ is a straight or branched alkylene group, an alkyleneoxyalkylene, or an alkylene polyoxyalkylene or a zwitterion; and furtherwherein R groups may be joined to form a heterocyclic nitrogen orphosphorus containing ring.
 3. The method claim 2, wherein A bothoccurrences of A in (III) are or contain nitrogen and R¹, R², R³, R⁴,R⁵, R⁶ and R⁷ are independently selected from the group consisting ofhydrogen; benzyl; oxyalkyl; a straight or branched C₁₋₃₀ alkyl group; aC₇₋₃₀ alkylbenzyl group; a C₇₋₃₀ arylalkyl group; a straight or branchedC₃₋₃₀ alkenyl group; a C₁₋₃₀ hydroxyalkyl group; a C₇₋₃₀hydroxyalkylbenzyl group; and a polyoxyalkylene group and furtherwherein R groups may be joined to form a heterocyclic nitrogen orphosphorus containing ring; and R⁸ is a straight or branched C₁₋₃₀alkylene, an alkylene oxyalkylene, or an alkylene polyoxyalkylene. 4.The method of claim 3, wherein R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ of (II) and(III) are independently selected from —H, a C₁₋₂₀ alkyl, —CH₂CH₂OH, andCH₂CH(CH₃)OH.
 5. The method of claim 1, wherein X is a hydroxide,halide, bicarbonate, carbonate, alkyl carbonate, alkoxide, carboxylateor a hydroxycarboxylate.
 6. The method of claim 3, wherein X is selectedfrom the group consisting of —Cl, —Br, —F or —I.
 7. The method of claim1, wherein X is selected from the group consisting of anionic phosphateesters, anionic thiophosphate esters, anionic phosphonate esters;anionic thiophosphonate esters; anionic diphosphonic acids,2-mercaptoethyl mercaptide, anionic 2-sulfanylethanol; anionic2-sulfanyl, propan-1-ol; anionic 2-sulfanylbutan-2-ol; anionic1-sulfanylbutanol-2-ol; and anionic glucaric acid and mixtures thereof.8. The method of claim 1, wherein A is selected from the groupconsisting of an imidazolium or pyridinium.
 9. The method of claim 8,wherein the pyridinium is an alkylpyridinium.
 10. The method of claim 8,wherein the ionic liquid is of the structure:

wherein R is a C₁₂-C₁₈ alkyl or alkenyl group and X is —OH, NH₂ orC(═O)R.
 11. The method of claim 7, wherein the ionic liquid is aphosphate ester or thiophosphate ester of the structure (IIA) or (IIB):

wherein R is an alkyl or RO(CH₂CH₂O)_(n)CH₂CH₂) and R″ and R′″ areindependently selected from —H and a C₁-C₂₀ alkyl.
 12. The method ofclaim 1, wherein the ionic liquid is a quaternary ammonium halide. 13.The method of claim 12, wherein the quaternary ammonium halide is of thestructure:

wherein the alkyl group contains from 1 to 20 carbon atoms.
 14. Themethod of claim 1, wherein the ionic liquid is an alkyl pyridine quat.15. The method of claim 14, wherein the alkyl pyridine quat containsmore than one pyrindyl ring.
 16. The method of claim 14, wherein thealkyl pyridine quat is of the structure:

wherein R is a C₁-C₁₈ alkyl or benzyl.
 17. The method of claim 1,wherein X is selected from the group consisting of anionic thiazoles,anionic triazoles and anionic thiadiazoles.
 18. The method of claim 1,wherein X is a carboxylate selected from the group consisting offormate, acetate, propionate, benzoate, n-butyrate, isobutyrate,pivalate, octanoate, laurate or is an anion of a C₁₈ fatty acid.
 19. Themethod of claim 1, wherein X is a hydroxycarboxylate selected from thegroup consisting of glycolate, lactate, citrate, glucarate, gluconateand tartrate.
 20. The method of claim 1, wherein the ionic liquid ispresent in a treatment composition containing a second corrosioninhibitor and further wherein the second corrosion inhibitor is not anionic liquid.
 21. The method of claim 20, wherein the anion of the ionicliquid is the same as the counter anion of the second corrosioninhibitor.
 22. The method of claim 1, wherein the acidic or aqueousliquid is crude oil, petroleum fuel or oil, a condensate, a distillateor cooling water.